1. Field of the Invention
The present invention relates to a fluid dynamic pressure bearing device, a spindle motor provided with the bearing device and a disk drive apparatus provided with the spindle motor.
2. Description of the Related Art
In recent years, a storage disk drive apparatus has been used in a personal computer, a car navigation and so forth. The storage disk drive apparatus is required to have increased density while also being small-sized, low-profile and lightweight. Demands for a high rotation number and a highly accurate rotational operation exist in a spindle motor used in rotating disks.
A conventional fluid dynamic pressure bearing device includes a conical dynamic pressure bearing unit for radially and axially supporting a shaft or a sleeve. As the shaft and the sleeve rotation relative to one another, a fluid dynamic pressure is generated in the lubricating fluid filled in a minute gap by the pumping action of dynamic pressure groove arrays of the conical dynamic pressure bearing unit. The shaft or the sleeve is radially and axially supported by the fluid dynamic pressure thus generated.
However, with the conventional dynamic pressure bearing device it is sometimes the case that a strong impact caused by external factors is applied to the fluid dynamic pressure bearing device in a tapering seal portion formed between the outer circumferential surface of an annular member and the inner circumferential surface of a seal member (or the inner circumferential surface of a rotating member such as a hub or the like in case of not employing the seal member). At this time, the width of a minute gap between the radial outermost portion of the annular member in a cross-section containing a center axis and the inner circumferential surface of the seal member (or the inner circumferential surface of the rotating member) becomes momentarily zero. As a result, the annular member and the seal member (or the rotating member) make contact with each other in the zero-width region. The lubricating fluid held in the tapering seal portion then momentarily leaks out from the zero-width region.